Alright i have a 88 firebird, TBI, WC T-5, And 118,000 miles on the car. Here is the problem. My speedo will work for 20-30 mins. before it starts to act up. In alaska i usually have to have the heater on, then after the heat has been on for a while the speedo will cut out intemittentaly. If i turn the heat off, and turn on the cold air it will start working after a min or two. Also tapping the dash under the speedo will get it to register if its not working. I was leaning towards a loose connection at the dash, but it is the heating of the dash that puzzles me If anyone has ideas of what to check, your insight will be greatly appreciated. - Russ

 

double post sorry please delete.